We have been talking with Roxul makers of the arguably the best batt insulation available. They are interested in being part of our project and of suggested that their newer product called Comfort Board would be a better way to reach our goals of R44. This product would be installed exterior to the building sheathing, on the outside of the framing. Exterior insulation like this makes for a continuous building envelope that is more efficient. With any luck Roxul will be able to support our project in a big way.
At long last we have come to a decision about insulating our slab. We installed 6” of EPS foam under the slab of the house with 3” of insulation between the slab and foundation walls. In the garage we put only 3” under and 1 1/2” insulation around the perimeter. Our crawl space will have 3” of rigid board installed on the walls with plywood over top to assist in mounting plumbing pipes and pumps.
With this system we are leaving all of the concrete exposed to the cold, choosing instead to bring the insulated layer around to the inside of the concrete. Our 12” thick wall will cover the 8” concrete wall and 3” of foam before the slab starts.